Technical Field
The present disclosure relates to a photographing optical lens assembly, an image capturing unit and an electronic device, more particularly to a photographing optical lens assembly and an image capturing unit applicable to an electronic device.
Description of Related Art
In recent years, with the popularity of electronic devices having camera functionalities, the demand of miniaturized optical systems has been increasing. The sensor of a conventional optical system is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical systems featuring better image quality.
A conventional optical system employed in a portable electronic product mainly adopts a five-element lens structure. Due to the popularity of mobile terminals with high-end specifications, such as smart phones, tablet personal computers and wearable apparatus, the requirements for high resolution and image quality of present compact optical systems increase significantly. However, the conventional optical systems cannot satisfy these requirements of the compact optical systems.
Other conventional compact optical systems with six-element lens structure are developed to enhance resolution and image quality. However, a back focal length of the optical system is too long to favorably keep the optical system compact. Furthermore, the refractive power of the optical system is unevenly distributed, which overly enlarges the incident angle of the light at the peripheral region of the image, thereby resulting in excessive stray light. Moreover, an image-side surface of the fourth lens element of the optical system is convex. Hence, it is unfavorable for adjusting the image difference between a central region and a peripheral region and reducing the aberration at the peripheral region of the image.